On Sunday, I was going EWR-ATL-IAH on the (5pm EWR-ATL flight). DL cancelled the 6:15, so it was a bonanza at the gate for the 5pm flight. I approached the GA, told her I would be willing to take the flight through MEM or wait until the next day if necessary. She actually oversold the JFK-IAH non-stop flight (at 830pm), gave me the $400 voucher, 2 meal vouchers, and a taxi voucher to get from EWR to JFK. She also thanked me profusely for being willing to help her out (this was before the arriving plane even got there).
This is now the third straight time in the past month I've VDB'd either at the ticket counter (CLE) or at the gate (ATL and EWR) before the arriving plane had even gotten there, nevermind boarded for the new flight. So much for the waiting till the flight closed. I'm not sure if it's a new trend, but it never hurts to be 1) courteous 2) knowledgeable (have alternates ready) and 3) flexible.
This is VDB SEASON, so take advantage of it! Oh, and I've always gotten ORC when I've gone in online and entered in the original ticket number.